Since a biosubstance itself shows little or no fluorescence in the visible light or near infrared region, imaged data have been obtained in the field of bioscience through various methods using a biosubstance and a fluorescent dye or a specific biosubstance including a biosubstance preliminarily labeled with a fluorescent dye in combination with an optical system in order to observe a biological phenomenon in a cellular stage or sub-cellular stage in vivo or in vitro, or to carry out laparography and to obtain an optical image of a diseased site through the projection in vivo.
Various optical analysis systems used in the field of bioscience use a selected fluorescent dye having an excitation wavelength and emission wavelength suitable for the observation of fluorescence depending on the light source and filter embedded therein, as a fundamental material or reagent.
Known optical analysis systems used frequently include those for research, such as a fluorescence microscope for observing cells, confocal microscope, flowcytometer, microarray, qualitative polymerase chain reaction (PCR) system, electrophoresis system for isolation and analysis of nucleic acids and proteins and a realtime in vivo imaging system; and those for diagnosis and treatment, such as an in vitro diagnosis system based on a nucleic acid and protein diagnosis kit (or biochip) combined with immunoassay or PCR analysis and statistical technology, a surgery die for image-guided surgery and an endoscope system. In addition, systems for use in novel applications and having a higher level of resolution and data processing capability have been developed continuously.
In general, most fluorescent dyes for use in labeling of a biomolecule, such as protein or peptide, include a structure such as anthranilate, 1-alkylthic isoindole, pyrrolinone, bimane, benzoxazole, benzimidazole, benzofurazan, naphthalene, coumarin, cyanine, stilbene, carbazole, phenanthridine, anthracenes, bodipy, fluorescein, eosin, rhodamine, pyrene, chrysene or acridine.
When screening a fluorescent dye structure applicable to the field of bioscience among the above mentioned fluorescent chromophores, it is generally important that most biosubstances emit strong fluorescence in a medium, i.e., aqueous solution and water-soluble buffer, containing the same and have an excitation wavelength and fluorescence wavelength suitable for a fluorescence device.
It is required for a dye mainly applicable to the field of bioscience to cause less photobleaching and quenching in aqueous solution or under a hydrophilic condition, to have a large molar extinction coefficient so that it may absorb a large amount of light, to be in the visible region or near infrared region of 500 nm or more away from the fluorescence region of a biosubstance itself, and to be stable under various pH conditions. However, there is a limitation in the structure of a dye applicable to labeling of a biosubstance while satisfying the above requirements.
Chromogens which meet the above requirements include cyanine, rhodamine, fluorescein, bodipy, coumarine, acridine and pyrene derivatives. In addition, such a dye may be used alone or a reactive group may be introduced thereto so as to be bound with a specific substituent in a biomolecular structure. Currently, xanthane-based fluoresceins and rhodamins and polymethine-based cyanine derivative dye compounds have been commercialized largely.
Particularly, a dye compound having a cyanine chromophore is advantageous in that it facilitates synthesis of compounds with various absorption/excitation wavelengths. In addition, such a dye compound has many advantages as follows and thus is used frequently for biological applications. It generally has excellent optical stability and pH stability, shows a narrow absorption and emission wavelength range, has a fluorescence region of 500-800 nm, which is not overlapped with the fluorescence region of a biomolecule itself, and allows easy analysis, and shows a high molar extinction coefficient with a slight difference depending on solvents and solubility characteristics.
Further, a dye compound having a cyanine chromophore may be used advantageously for an optical filter for an image display device or a resin composition for laser welding. A compound which shows high-intensity absorption to specific light has been used widely for an optical filter for an image display device, such as a liquid crystal display device, plasma display panel, electroluminescence display, cathode tube display device or a fluorescence display tube, or for an optical element of an optical recording medium such as DVD±R. It is required for an optical filter to have a function of selectively absorbing light with an undesired wavelength. In addition to this, it is required to absorb light with a wavelength of 480-500 nm and 540-560 nm in order to prevent reflection of external light, such as light from a fluorescence lamp, or glare. Further, it is required to have a function of selectively absorbing light with a wavelength in the near infrared region in order to improve the quality of an image.
Thus, there has been a continuous need for developing a novel dye having excellent optical stability and pH stability and showing a high molar extinction coefficient with a narrow absorption/emission wavelength range in a specific wavelength region so that it may be applied advantageously to various industrial fields.